Consciousness is the state or quality of awareness, or, of being aware of an external object or something within oneself. It has been defined variously in terms of sentience, awareness, subjectivity, the ability to experience or to feel, wakefulness, having a sense of selfhood or soul, the fact that there is something “that it is like” to “have” or “be” it, and the executive control system of the mind, or the state or quality of awareness, or, of being aware of an external object or something within oneself. In contemporary philosophy its definition is often hinted at via the logical possibility of its absence, the philosophical zombie, which is defined as a being whose behavior and function are identical to one’s own yet there is “no-one in there” experiencing it.
Despite the difficulty in definition, many philosophers believe that there is a broadly shared underlying intuition about what consciousness is. As Max Velmans and Susan Schneider wrote in The Blackwell Companion to Consciousness: "Anything that we are aware of at a given moment forms part of our consciousness, making conscious experience at once the most familiar and most mysterious aspect of our lives